Are you annoyed that a stranger cut you off in traffic? Are you aggravated that you have to work late?

Here’s something else to get angry about — holding in that anger can give you a headache, according to research from Saint Louis University.

“We found that holding in anger is the biggest predictor of headaches, among the group of patients we studied,” said Dr. Robert Nicholson, assistant professor of community and family medicine at the university and principle investigator of the study. “Anger might be one of the many things that interact to trigger headaches.”

Of the 422 adults studied, 171 suffered from headaches. Nicholson examined how angry a person was, how much he or she internalized anger and the severity and frequency of the headaches. He also considered whether the individual was anxious or depressed: both have been linked to headaches, he said.

Nicholson found that repressed anger, even more than depression or anxiety, was more likely to cause headaches.

However, there are times when expressing anger isn’t recommended, he noted.

“It isn’t always the best thing,” Nicholson said. “Yelling at your boss could cost you your job. Making an obscene gesture at a driver who cut you off in traffic could lead to road rage.”

Nicholson suggests the following strategies to cope with anger:

• Breathe deeply. When you’re angry, your body becomes tense. Breathing deeply will help lower your internal anger meter.

• Know why you feel angry. Think like a detective and track down clues about the kinds of situations, people and events that trigger your anger.

• Express yourself, but make sure it won’t do more harm than good in the long run. In some cases, you can tell others how you feel in an assertive, non-confrontational way, which makes you feel better and lets others know what they’ve done to annoy you. However, if expressing your anger could cause more problems, vent to a friend instead of the person who has wronged you.

• Change your environment. Take a five-minute walk or create a mental escape by turning on the radio and singing out loud if you’re caught in traffic.

• Acknowledge that sometimes life is unfair.

• Let go of things that are beyond your control. Getting angry doesn’t fix the situation and can make you feel worse.

• Forgive. This may be the most difficult coping strategy to master because it involves making a conscious choice not to hold something against someone.

“Whether the wound is from someone else or is self-inflicted, the greatest power you have is the ability to forgive and let it go,” Nicholson said. “It won’t change the past, but neither will being angry.”